In earlier days most of the programmers liked it – having the data type as a prefix for the variable name and using m_ as prefix for member variables. Eg:

string m_sName;

int nAge;

However, in .NET coding standards, this is not recommended. Usage of data type and m_ to represent member variables should not be used. All variables should use camel casing.

Some programmers still prefer to use the prefix m_ to represent member variables, since there is no other easy way to identify a member variable.

6.Use Meaningful, descriptive words to name variables. Do not use abbreviations.

Good:

string address

int salary

Not Good:

string nam

string addr

int sal

7.Do not use single character variable names like i, n, s etc. Use names like index, temp

One exception in this case would be variables used for iterations in loops:

for ( int i = 0; i < count; i++ )

{

…

}

If the variable is used only as a counter for iteration and is not used anywhere else in the loop, many people still like to use a single char variable (i) instead of inventing a different suitable name.

8.Do not use underscores (_) for local variable names.

9.All member variables must be prefixed with underscore (_) so that they can be identified from other local variables.

10.Do not use variable names that resemble keywords.

11.Prefix boolean variables, properties and methods with “is” or similar prefixes.

13.Use appropriate prefix for the UI elements so that you can identify them from the rest of the variables.

There are 2 different approaches recommended here.

a.Use a common prefix ( ui_ ) for all UI elements. This will help you group all of the UI elements together and easy to access all of them from the intellisense.

b.Use appropriate prefix for each of the ui element. A brief list is given below. Since .NET has given several controls, you may have to arrive at a complete list of standard prefixes for each of the controls (including third party controls) you are using.

Control

Prefix

Label

lbl

TextBox

txt

DataGrid

dtg

Button

btn

ImageButton

imb

Hyperlink

hlk

DropDownList

ddl

ListBox

lst

DataList

dtl

Repeater

rep

Checkbox

chk

CheckBoxList

cbl

RadioButton

rdo

RadioButtonList

rbl

Image

img

Panel

pnl

PlaceHolder

phd

Table

tbl

Validators

val

14.File name should match with class name.

For example, for the class HelloWorld, the file name should be helloworld.cs (or, helloworld.vb)

6.Do not hardcode numbers. Use constants instead. Declare constant in the top of the file and use it in your code.

However, using constants are also not recommended. You should use the constants in the config file or database so that you can change it later. Declare them as constants only if you are sure this value will never need to be changed.

7.Do not hardcode strings. Use resource files.

8.Convert strings to lowercase or upper case before comparing. This will ensure the string will match even if the string being compared has a different case.

if ( name.ToLower() == “john” )

{

//…

}

9.Use String.Empty instead of “”

Good:

If ( name == String.Empty )

{

// do something

}

Not Good:

If ( name == “” )

{

// do something

}

10.Avoid using member variables. Declare local variables wherever necessary and pass it to other methods instead of sharing a member variable between methods. If you share a member variable between methods, it will be difficult to track which method changed the value and when.

11.Use enum wherever required. Do not use numbers or strings to indicate discrete values.

Good:

enum MailType

{

Html,

PlainText,

Attachment

}

void SendMail (string message, MailType mailType)

{

switch ( mailType )

{

case MailType.Html:

// Do something

break;

case MailType.PlainText:

// Do something

break;

case MailType.Attachment:

// Do something

break;

default:

// Do something

break;

}

}

Not Good:

void SendMail (string message, string mailType)

{

switch ( mailType )

{

case “Html”:

// Do something

break;

case “PlainText”:

// Do something

break;

case “Attachment”:

// Do something

break;

default:

// Do something

break;

}

}

12.Do not make the member variables public or protected. Keep them private and expose public/protected Properties.

13.The event handler should not contain the code to perform the required action. Rather call another method from the event handler.

14.Do not programmatically click a button to execute the same action you have written in the button click event. Rather, call the same method which is called by the button click event handler.

15.Never hardcode a path or drive name in code. Get the application path programmatically and use relative path.

16.Never assume that your code will run from drive “C:”. You may never know, some users may run it from network or from a “Z:”.

17.In the application start up, do some kind of “self check” and ensure all required files and dependancies are available in the expected locations. Check for database connection in start up, if required. Give a friendly message to the user in case of any problems.

18.If the required configuration file is not found, application should be able to create one with default values.

19.If a wrong value found in the configuration file, application should throw an error or give a message and also should tell the user what are the correct values.

20.Error messages should help the user to solve the problem. Never give error messages like “Error in Application”, “There is an error” etc. Instead give specific messages like “Failed to update database. Please make sure the login id and password are correct.”

21.When displaying error messages, in addition to telling what is wrong, the message should also tell what should the user do to solve the problem. Instead of message like “Failed to update database.”, suggest what should the user do: “Failed to update database. Please make sure the login id and password are correct.”

22.Show short and friendly message to the user. But log the actual error with all possible information. This will help a lot in diagnosing problems.

23.Do not have more than one class in a single file.

24.Have your own templates for each of the file types in Visual Studio. You can include your company name, copy right information etc in the template. You can view or edit the Visual Studio file templates in the folder C:\Program Files\Microsoft Visual Studio 8\Common7\IDE\ItemTemplatesCache\CSharp\1033. (This folder has the templates for C#, but you can easily find the corresponding folders or any other language)

25.Avoid having very large files. If a single file has more than 1000 lines of code, it is a good candidate for refactoring. Split them logically into two or more classes.

26.Avoid public methods and properties, unless they really need to be accessed from outside the class. Use “internal” if they are accessed only within the same assembly.

27.Avoid passing too many parameters to a method. If you have more than 4~5 parameters, it is a good candidate to define a class or structure.

28.If you have a method returning a collection, return an empty collection instead of null, if you have no data to return. For example, if you have a method returning an ArrayList, always return a valid ArrayList. If you have no items to return, then return a valid ArrayList with 0 items. This will make it easy for the calling application to just check for the “count” rather than doing an additional check for “null”.

29.Use the AssemblyInfo file to fill information like version number, description, company name, copyright notice etc.

30.Logically organize all your files within appropriate folders. Use 2 level folder hierarchies. You can have up to 10 folders in the root folder and each folder can have up to 5 sub folders. If you have too many folders than cannot be accommodated with the above mentioned 2 level hierarchy, you may need re factoring into multiple assemblies.

1.Make sure you have a good logging class which can be configured to log errors, warning or traces. If you configure to log errors, it should only log errors. But if you configure to log traces, it should record all (errors, warnings and trace). Your log class should be written such a way that in future you can change it easily to log to Windows Event Log, SQL Server, or Email to administrator or to a File etc without any change in any other part of the application. Use the log class extensively throughout the code to record errors, warning and even trace messages that can help you trouble shoot a problem.

2.If you are opening database connections, sockets, file stream etc, always close them in the finally block. This will ensure that even if an exception occurs after opening the connection, it will be safely closed in the finally block.

3.Declare variables as close as possible to where it is first used. Use one variable declaration per line.

4.Use StringBuilder class instead of String when you have to manipulate string objects in a loop. The String object works in weird way in .NET. Each time you append a string, it is actually discarding the old string object and recreating a new object, which is a relatively expensive operations.

Consider the following example:

public string ComposeMessage (string[] lines)

{

string message = String.Empty;

for (int i = 0; i < lines.Length; i++)

{

message += lines [i];

}

return message;

}

In the above example, it may look like we are just appending to the string object ‘message’. But what is happening in reality is, the string object is discarded in each iteration and recreated and appending the line to it.

If your loop has several iterations, then it is a good idea to use StringBuilder class instead of String object.

See the example where the String object is replaced with StringBuilder.

2.Never access database from the UI pages. Always have a data layer class which performs all the database related tasks. This will help you support or migrate to another database back end easily.

3.Use try-catch in your data layer to catch all database exceptions. This exception handler should record all exceptions from the database. The details recorded should include the name of the command being executed, stored proc name, parameters, connection string used etc. After recording the exception, it could be re thrown so that another layer in the application can catch it and take appropriate action.

4.Separate your application into multiple assemblies. Group all independent utility classes into a separate class library. All your database related files can be in another class library.

1.Do not use session variables throughout the code. Use session variables only within the classes and expose methods to access the value stored in the session variables. A class can access the session using System.Web.HttpCOntext.Current.Session

2.Do not store large objects in session. Storing large objects in session may consume lot of server memory depending on the number of users.

3.Always use style sheet to control the look and feel of the pages. Never specify font name and font size in any of the pages. Use appropriate style class. This will help you to change the UI of your application easily in future. Also, if you like to support customizing the UI for each customer, it is just a matter of developing another style sheet for them

1.Do not write comments for every line of code and every variable declared.

2.Use // or /// for comments. Avoid using /* … */

3.Write comments wherever required. But good readable code will require very less comments. If all variables and method names are meaningful, that would make the code very readable and will not need many comments.

4.Do not write comments if the code is easily understandable without comment. The drawback of having lot of comments is, if you change the code and forget to change the comment, it will lead to more confusion.

5.Fewer lines of comments will make the code more elegant. But if the code is not clean/readable and there are less comments, that is worse.

6.If you have to use some complex or weird logic for any reason, document it very well with sufficient comments.

7.If you initialize a numeric variable to a special number other than 0, -1 etc, document the reason for choosing that value.

8.The bottom line is, write clean, readable code such a way that it doesn’t need any comments to understand.

9.Perform spelling check on comments and also make sure proper grammar and punctuation is used.

1.Never do a ‘catch exception and do nothing’. If you hide an exception, you will never know if the exception happened or not. Lot of developers uses this handy method to ignore non significant errors. You should always try to avoid exceptions by checking all the error conditions programmatically. In any case, catching an exception and doing nothing is not allowed. In the worst case, you should log the exception and proceed.

2.In case of exceptions, give a friendly message to the user, but log the actual error with all possible details about the error, including the time it occurred, method and class name etc.

3.Always catch only the specific exception, not generic exception.

Good:

void ReadFromFile ( string fileName )

{

try

{

// read from file.

}

catch (FileIOException ex)

{

// log error.

//re-throw exception depending on your case.

throw;

}

}

Not Good:

void ReadFromFile ( string fileName )

{

try

{

// read from file.

}

catch (Exception ex)

{

// Catching general exception is bad… we will never know whether

// it was a file error or some other error.

// Here you are hiding an exception.

// In this case no one will ever know that an exception happened.

return “”;

}

}

4.No need to catch the general exception in all your methods. Leave it open and let the application crash. This will help you find most of the errors during development cycle. You can have an application level (thread level) error handler where you can handle all general exceptions. In case of an ‘unexpected general error’, this error handler should catch the exception and should log the error in addition to giving a friendly message to the user before closing the application, or allowing the user to ‘ignore and proceed’.

5.When you re throw an exception, use the throw statement without specifying the original exception. This way, the original call stack is preserved.

Good:

catch

{

// do whatever you want to handle the exception

throw;

}

Not Good:

catch (Exception ex)

{

// do whatever you want to handle the exception

throw ex;

}

6.Do not write try-catch in all your methods. Use it only if there is a possibility that a specific exception may occur and it cannot be prevented by any other means. For example, if you want to insert a record if it does not already exists in database, you should try to select record using the key. Some developers try to insert a record without checking if it already exists. If an exception occurs, they will assume that the record already exists. This is strictly not allowed. You should always explicitly check for errors rather than waiting for exceptions to occur. On the other hand, you should always use exception handlers while you communicate with external systems like network, hardware devices etc. Such systems are subject to failure anytime and error checking is not usually reliable. In those cases, you should use exception handlers and try to recover from error.

7.Do not write very large try-catch blocks. If required, write separate try-catch for each task you perform and enclose only the specific piece of code inside the try-catch. This will help you find which piece of code generated the exception and you can give specific error message to the user.

Write your own custom exception classes if required in your application. Do not derive your custom exceptions from the base class SystemException. Instead, inherit from ApplicationException.